Removable barrel and hand guard for modular rifles

ABSTRACT

A system for connecting a barrel to an upper receiver of a modular rifle, the upper receiver having an upper receiver extension. The system comprises an upper receiver coupler having a first opening for receiving the upper receiver extension, which is removably secured in the first opening. The system includes a barrel coupler and a gas tube for attaching to a forward segment of the barrel, extending rearwardly along the barrel, passing through a second opening of the barrel coupler and coupled to a gas port that extends from the upper receiver and into the upper receiver coupler. The gas tube is shorter than the barrel. The barrel passes through and is removably secured within a third opening of the barrel coupler; passes through the first opening of the upper receiver coupler and into the upper receiver extension. The upper receiver coupler and the barrel coupler are removably connected.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 119(e) to the provisional patent application filed on Apr. 21, 2017 and assigned application No. 62/488,458. This provisional patent application is incorporated herein in its entirety.

FIELD OF THE INVENTION

A method, system, and kit related to a removable and replaceable barrel kit with a gas tube for modular rifles.

BACKGROUND OF THE INVENTION

M16 and AR15 rifles are air-cooled, gas-operated, magazine-fed assault rifles. These rifles are the primary assault weapons used by military and police forces.

A gas-operated rifle uses a portion of the high-pressure gas formed as the ammunition round travels through the barrel to supply energy to operate the auto-loading feature of the rifle. The high—pressure gas powers a mechanism to extract the spent casing and chamber a new cartridge. Energy from the gas is harnessed through either a port in the barrel or a trap in the muzzle. This high-pressure gas travels through a gas tube that is located parallel to the barrel and upon exiting the tube impinges on a surface such as a piston head to provide motion for unlocking the action, extracting the spent casing, ejecting the spent casing, cocking the hammer or striker, chambering a fresh cartridge, and finally locking the action.

Such a modular rifle is illustrated in FIG. 1. As shown in FIG. 2, the rifle comprises a lower receiver assembly 1 conveniently separable from an upper receiver assembly 2. The lower and upper receiver assemblies 1 and 2 are connected using push pins with the pins carried by the lower receiver assembly 1 and extending through openings (not visible in FIG. 2) in the upper receiver assembly 2.

The lower receiver assembly 1 contains a lower receiver, fire control components, and a buffer assembly included in the butt-stock. These components are not separately designated in FIG. 2 and are not pertinent to the structure and function of the present invention. Instead, the present invention relates generally to the upper receiver assembly 2 and its components.

Prior art FIG. 3 illustrates the upper receiver assembly 2, comprising an upper receiver 3 and a hand guard 4 surrounding a barrel 5. The barrel 5 is affixed to the upper receiver 3 using a barrel nut that is obscured from view in FIG. 3 but shown in FIG. 4.

Prior art FIG. 4 illustrates the upper receiver assembly 2 with the hand guard 4 removed to expose a barrel nut 6, a stock gas tube 7 and a gas block 8 that holds the stock gas tube 7 in place. The barrel 5 and the gas block 8 each define a small opening through which gas passes from the barrel, through the gas block, and into the stock gas tube 7.

In the prior art modular rifles of FIGS. 1-4, the barrel 5 is affixed to the upper receiver 3 with the barrel nut 6 and this arrangement requires specialized tools and fixtures to remove and attach the barrel. For example, if the user wishes to change to a barrel of a different length. The prior art design makes it nearly impossible to remove the barrel in the field without use of these tools. Removal also requires a significant amount of time and familiarity with intricate mechanisms of the rifle.

BRIEF DESCRIPTION OF THE FIGURES

The forgoing and other features of the present invention will be apparent to one skilled in the art to which the present invention relates upon consideration of the description of the invention with reference to the accompanying drawings. The use of the same reference numeral in the various figures refers to the same element.

FIG. 1 illustrates an exemplary prior art AR15/AR10 modular rifle.

FIG. 2 illustrates an exploded view of the prior art AR15/AR10 modular rifle of FIG. 1.

FIGS. 3 and 4 illustrate components of the prior art upper receiver assembly of FIG. 2.

FIG. 5 illustrates an exploded view of components of an upper receiver coupler and a barrel coupler.

FIG. 6 illustrates the upper receiver and FIG. 7 the upper receiver with the upper receiver coupler attached thereto.

FIG. 8 illustrates the upper receiver coupler.

FIG. 9 illustrates the barrel coupler and the attached barrel.

FIG. 10 illustrates the barrel coupler.

FIGS. 11 and 12 illustrate the barrel with different length gas tubes.

FIG. 13 illustrates the barrel coupler, the barrel, and the hand guard.

FIG. 14 illustrates an exploded view of the upper receiver coupler (attached to the upper receiver) and the barrel coupler (attached to the barrel and hand guard).

FIG. 15 illustrates the barrel coupler mated to the upper receiver coupler.

FIG. 16 illustrates the barrel coupler attached to the upper receiver coupler.

FIG. 17 illustrates an AR15/AR10 rifle with the components of the present invention attached thereto.

FIG. 18 illustrates another embodiment of the barrel coupler and upper receiver coupler.

FIGS. 19-21 illustrate three different gas tubes.

FIGS. 22 and 23 illustrate different views of details of the hook and lever of the barrel coupler.

FIG. 24 illustrates an alternative embodiment of the upper receiver coupler.

FIG. 25 illustrates a prior art barrel and gas tube.

FIG. 26 illustrates a prior art upper receiver.

FIG. 27 illustrates a prior art gas key and bolt carrier.

FIG. 28 illustrates a gas key and bolt carrier according to the present invention.

FIG. 29 illustrates a modified upper receiver according to the present invention.

FIG. 30 illustrates a segment of an upper receiver and a protruding gas key.

FIG. 31 illustrates a barrel and gas tube according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Before describing in detail the particular methods and apparatuses related to a removable barrel and hand guard for modular rifles, it should be observed that the present invention resides primarily in a novel and non-obvious combination of elements and process steps. So as not to obscure the disclosure with details that will be readily apparent to those skilled in the art, certain conventional elements and steps have been presented with lesser detail, while the drawings and the specification describe in greater detail other elements and steps pertinent to understanding the inventions.

The presented embodiments are not intended to define limits as to the structures, elements or methods of the inventions, but only to provide exemplary constructions. The embodiments are permissive rather than mandatory and illustrative rather than exhaustive.

The components of the present invention when installed in a rifle allow the rifle user to easily and quickly remove the barrel without specialized tools and replace the removed barrel with a barrel of a different length. As is known by those skilled in the art, a longer barrel allows the ammunition round to exit the barrel with a greater velocity and thus travel farther (i.e., have a longer range) than a round shot from a shorter barrel.

Advantages of the present invention include at least: allowing the rifle barrel to be easily removed to store or transport the rifle in a smaller space; allowing the user to easily remove and replace the barrel with a different length barrel; allowing conversion of the rifle to a different caliber; and, simplifying cleaning of the weapon as specialized tools are not required to disassemble the rifle. With regard to different barrel lengths, a sniper prefers a longer rifle barrel while a shorter barrel is desired in close-quarter combat.

The invention also permits the user to use any one of many different available hand guards. Alternatively, the barrel coupler of the present invention may be supplied with a hand guard permanently integrated with the barrel coupler. In this latter embodiment the barrel and hand guard can both be removed from the rifle as one unit without the user of tools.

The components of the present invention may be installed on any rifle or weapon having an appropriately styled barrel and receiver interface.

The components of the invention may also be considered a kit for adding and/or replacing the components of an existing rifle to allow the user to then easily and conveniently exchange a barrel of a first length for a barrel of a second length. The kit components can be installed on an existing rifle without any permanent modifications to the rifle. Alternatively, certain of the invention components can be integrated into a new rifle as it is manufactured, e.g., the upper receiver coupler integral with the upper receiver and/or the barrel coupler integral with the barrel.

The components of the invention generally comprise: an upper receiver coupler for attaching to an upper receiver of an existing rifle and a barrel coupler for attaching to a barrel of the existing rifle. The upper receiver coupler and the barrel coupler are removably joined or latched together using components attached to the upper receiver coupler, to the barrel coupler, and/or to both. Further, the invention comprises a novel gas tube that is attached to the barrel, passes through the upper receiver coupler and the barrel coupler, and via a gas tube extension attaches to the rifle upper receiver.

FIG. 5 is an exploded view illustrating an upper receiver coupler 100 and a barrel coupler 103 and their associated components. With the upper receiver coupler attached to the upper receiver, as described elsewhere herein, and the barrel coupler attached to the barrel, as described elsewhere herein, coupling the upper receiver coupler and the barrel coupler thereby attaches the barrel to the upper receiver to form a continuous path for the ammunition round.

Additionally, when the upper receiver coupler and the barrel coupler are joined, a gas tube running parallel to the barrel extends from a forward end of the barrel, passes through both couplers, and is received within the upper receiver of the rifle. Gas flowing through this path actuates various rifle functions as described above.

Turing to FIG. 6, it illustrates the conventional upper receiver 3 further comprising a threaded upper receiver extension 3A and a gas port 3B. In a prior art rifle, the barrel is received within the upper receiver extension 3A and a barrel nut (not shown) holds the barrel within the upper receiver extension. A groove 3C receives a tab on the barrel (not shown) to properly align the barrel to the upper receiver.

With reference to FIGS. 5, 6, and 7, to attach the upper receiver coupler 100 to the upper receiver 3, the threaded upper receiver extension 3A is inserted into an opening 10A defined in an upper receiver plate 10. Internal threads 11A of a star nut 11 threadably engage external threads of the upper receiver extension 3A, and the star nut 11 is tightened to fixedly join the upper receiver coupler 100 to the upper receiver 3. FIG. 7 illustrates the final configuration.

Semicircular grooves 16 in an outer circumference of the star nut 11 receive mating protrusions of a tool (not shown) for tightening the star nut 11. However, this feature is not a required element of the invention, instead it is merely a convenient technique for tightening the star nut 11.

FIG. 8 also illustrates certain components and features of the upper receiver coupler 100 including the upper receiver plate 10 and the star nut 11. The remainder of the illustrated components is described below.

In an alternative embodiment, in lieu of using the star nut 11, the upper receiver plate 10 comprises internal threads 25 (see FIG. 24) that threadably engage mating threads 3D on the upper receiver extension 3A of FIG. 6.

With reference to FIGS. 5 and 9, to position the barrel 5 within the barrel coupler 103, the barrel is received within an opening 103A that extends through the barrel coupler. A raised segment of the barrel, referred to as a collar (see a collar 5A in FIGS. 9, 11, and 12), is disposed within the opening 103A and a rear surface of the collar 5A abuts an internal surface of the barrel coupler 103.

With continued reference to FIGS. 5 and 9, set screws 17 distributed around a circumference of a barrel plate 14 are urged against the barrel 5 to hold the barrel within the barrel coupler 103. In one embodiment the set screws are spaced at 120 degrees although only one set screw 17 is illustrated in FIG. 5. Additionally, when the barrel coupler and the upper receiver coupler are mated, the barrel flange is captured and held in place between the mated barrel coupler and the upper receiver coupler. Also, in one embodiment the groove 3C of the upper receiver extension 3A of FIG. 6 receives a tab (not shown) of the barrel to align the barrel in the upper receiver. Finally, the mated couplers exert additional forces on the barrel to secure the barrel within the barrel coupler.

As can be seen in FIG. 9, a barrel segment 5B of the barrel 5 extends beyond a rear surface of the barrel coupler 103. The barrel segment 5B further extends into the opening 10A (see FIGS. 5, 7, and 8) of the coupler plate 10 when the upper receiver coupler and the barrel coupler are mated.

In lieu of using the set screws 17, the barrel can be held in place within the barrel coupler 103 by a compression fitting comprising a slot defined in the barrel plate 14 and a tension screw to close the slot after the barrel is inserted. Alternatively, an end of the barrel comprises a split cone feature with an outside-threaded nut for threading into mating threads extending from a rear surface of the barrel plate.

Returning to FIG. 5, in addition to the barrel plate 14, the barrel coupler 103 further comprises hooks 12, levers 13 for operating the hooks 12, and a barrel plate extension 14A. Only one hook 12 and lever 13 is illustrated in FIG. 5 as the opposing hook and lever is not visible in FIG. 5.

The hooks 12 and levers 13 are held together by pins not illustrated in FIG. 5 but depicted as a pin 140 in FIGS. 22 and 23. With reference to FIG. 5, the pin is held in position by a set screw 22, again, with only one illustrated in FIG. 5.

With the barrel coupler 103 in contact with the upper receiver coupler 100, exerting an inwardly-directed force on the levers 13 forces the hooks 12 to each engage a hardened pin 21 within each recess 10B in the upper receiver plate 10. This action locks the barrel plate 14 to the receiver plate 10 and thereby locks the barrel coupler 103 to the upper receiver coupler 100. Another hook, lever, recess and pin are disposed on an opposing side of the respective barrel plate and the upper receiver plate and thus are hidden from view in FIG. 5.

The illustrated pin 21 is held in position by action of a set screw 23.

With the barrel 5 attached to the barrel coupler 103 with the set screws 17, the barrel coupler 103 attached to the upper receiver coupler 100 with the hooks 12, and the upper receiver coupler attached to the upper receiver 3 with the star nut 11, the barrel is thereby coupled to upper receiver to provide a path for the round as it exits the upper receiver, enters and passes through the barrel segment 5B (see FIG. 9) and the barrel 5, and exits from a forward end of the barrel 5.

With this invention the barrel 5 can be easily and quickly changed by operating the levers 13 to release the hooks 12 and thereby separate the upper receiver coupler 100 from the barrel coupler 103 and loosening the set screws 17. This operation is much simpler than the required operations to remove the barrel in a prior art rifle.

With reference to FIG. 5, when the barrel coupler 103 is brought into contact with the upper receiver coupler 100, an alignment pin 19 extending rearwardly from a rear surface of the barrel plate 14 is received within an opening 20 in a forward-facing surface of the upper receiver plate 10 for aligning the upper receiver coupler 100 and the barrel coupler 103.

FIG. 10 is a rear view of the barrel coupler 103. In particular, this view shows an opening 29 through which a primary gas tube 33 passes, as described below.

As described above, a gas-operated rifle uses some of the high-pressure gas generated as the ammunition round travels through the barrel to supply energy to operate the auto-loading feature of the rifle. In the present invention, a high-pressure gas path extends from an entry point of the gas tube on the barrel 5, along the barrel, through the barrel coupler 103, through the upper receiver coupler 100 and finally to the upper receiver 3.

As can be seen in FIGS. 5 and 9, a primary gas tube 33 extends forward from the barrel plate 14 runs parallel to the barrel 5 and connects to the barrel 5 at the gas block 8.

Working toward the butt stock of the rifle and beginning at the barrel plate 14, the primary gas tube 33 passes through the opening 29 (see FIG. 10) in the barrel plate 14. A rearward segment 33A of the primary gas tube 33 (see FIGS. 5 and 9) extends rearward out from the opening 29 in the barrel plate and through an opening 36 (see FIG. 8) in the receiver plate 10. An end 33B of the rearward segment 33A mates with a coupler 34 (that is, when the upper receiver coupler 100 and the barrel coupler 103 are coupled) that is in turn connected to a gas tube extension 35 (see FIGS. 5 and 8).

To avoid interference between the rearward segment 33A of the primary gas tube 33 and the upper receiver coupler 100 and its associated components, the rearward segment 33A is disposed within one of the semicircular grooves 16 of the star nut 11.

An end 35A of the gas tube extension 35 (both of which are depicted in FIG. 5) is received within the gas port 3B of the upper receiver 3 as illustrated in FIG. 6.

FIG. 11 illustrates the barrel 5 with a stock or stock gas tube 7 installed in the gas block 8.

FIG. 12 illustrates the barrel 5 with the shortened primary gas tube 33, i.e., shorter than the stock gas tube 7, installed in the gas block 8. The shortened gas tube is required due to presence of the receiver coupler 100 and the barrel coupler 103 in the gas flow path between the gas block 8 and the gas port 3B in the upper receiver 3.

FIG. 13 illustrates the hand guard 4 as mated with the barrel coupler 103 and covering a segment of the barrel 5 and the entire length of the primary gas tube 33. To attach the hand guard 4, inside threads of the hand guard threadably engage outside matching threads of the barrel plate extension 14A depicted at least in FIGS. 5 and 9.

FIG. 13 also reveals that the hand guard 4 and the barrel 5, when affixed to the barrel coupler 103, can be removed from the rifle as a unitary structure by simply separating the barrel coupler 103 from the upper receiver coupler 100.

FIG. 14 illustrates the upper receiver coupler 100 (and certain ones of its attached components) in position to mate with the barrel coupler 103 (and certain ones of its attached components).

To mate the upper receiver coupler 100 and the barrel coupler 103, (see FIGS. 5 and 14 in particular) the opening 10A in the upper receiver plate 10 is aligned with the barrel segment 5B, the pin 19 of the barrel coupler is aligned with the opening 20 in the receiver coupler, and the rearward segment 33A of the gas tube is aligned with the coupler 34. The upper receiver coupler and the barrel coupler are brought into contact and by the application of an inwardly directed force on the levers 13, the hooks 12 on the barrel coupler are locked around the pins 21 in the recesses 10B of the upper receiver coupler.

FIG. 15 illustrates the mated upper receiver coupler 100 and the barrel coupler 103 with the hooks 12 in an open position.

FIG. 16 illustrates the coupled upper receiver coupler 100 and the barrel coupler 103 with the hooks 12 in a closed position.

FIG. 17 illustrates an AR15/AR10 110 depicting the upper receiver coupler 100 and the barrel coupler 103 of the present invention.

FIG. 18 illustrates another embodiment of the present invention comprising an upper receiver coupler 111 for mating with a barrel coupler 113. The upper receiver coupler 111 defines recesses 120 each for receiving a hook 122 (in lieu of the hook 12 of other embodiments) to attach the upper receiver coupler 111 to the barrel coupler 113.

Each hook 122 comprises a head 130 affixed to a shaft 132 at a first end thereof. A second end of the shaft 132 terminates in a ring 133 concentrically mounted on a pin 136 that is in turn attached to or captured within a barrel plate 137. The hooks 122 are pivoted into the recesses 120 to lock the upper receiver coupler 111 and the barrel coupler 113 together.

Pivoting of the hooks 122 out of the recesses 120 permits separation of the upper receiver coupler 111 and the barrel coupler 113. Only one of the hooks 122 is depicted in its entirety in FIG. 18, another hook 122 and its associated components is hidden from view in FIG. 18.

In one embodiment the head 130 threadably engages mating threads (not shown) on the shaft 132. The coupling force exerted by the hook 122 on the upper receiver coupler 111 is adjusted by turning the head 130 on the mating threads of the shaft 132.

FIG. 19 illustrates a stock gas tube 7. FIG. 20 illustrates the shortened primary gas tube 33 connected to the gas tube extension 35 for use with the couplers of the present invention. FIG. 21 illustrates an exploded view of the primary gas tube 33 and the gas tube extension 35.

FIG. 22 is a close-up view of the hook 12 and the lever 13 including a pivot pin 140 and a tension adjustment screw 142. Turning the screw 142 adjusts (increasing or decreasing) the force exerted by the hook 12 for holding the upper receiver coupler 100 and the barrel coupler 103 together and for increasing or decreasing the distance between the two couplers.

FIG. 23 depicts the hook 12, the pivot pin 140 and the tension adjustment screw 142.

Conventional after-market removable barrels comprise a gas tube (also referred to as a barrel gas tube) with a portion of the barrel gas tube (referred to as a projecting gas tube segment) extending beyond an end of the barrel. See prior art FIG. 25 that illustrates a stock or prior art barrel gas tube 200 with a segment 200A extending beyond the barrel.

When attaching the barrel to the receiver, this projecting gas tube segment is inserted into a gas key (element 205 in the prior art FIG. 27) of the receiver, e.g., the receiver of an AR15/AR10 rifle. When the barrel is separated from the upper receiver, the projecting segment can be easily broken off from the barrel gas tube, especially in a situation where the rifle user must quickly reassemble the rifle. For example, when the user replaces one barrel with another barrel.

The protruding gas tube can also be damaged when the user is transporting the rifle in a disassembled condition, as the protruding tube extends beyond the “safety” of the heavy barrel. Also, the heavy barrel may exert a force on the extending tube when set down or dropped.

Of course, if the projecting segment is severed from the barrel gas tube the weapon is inoperable.

FIG. 26 depicts a conventional receiver 203 and an opening 203A for receiving a prior art barrel gas tube that extends beyond the replaceable barrel as shown in FIG. 25.

FIG. 27 depicts a stock (prior art) gas key 205 attached to a stock bolt carrier 207.

The present embodiment eliminates the projecting gas tube segment 200A of FIG. 25 and thereby the possibility of any damage to the replaceable barrel.

To eliminate or shorten the projecting gas tube segment, the receiver/gas key must be modified to accept the shorter barrel gas tube. See FIG. 28 illustrating a gas key 210 for use with the shorter barrel gas tube, comprising a bolt carrier attachment interface 210A for attaching the gas key 210 to the stock bolt carrier 207, and a gas tube attachment interface 210B for receiving the barrel gas tube. As can be seen by comparing the prior art FIG. 27 and with the inventive FIG. 28, the gas key 210 has a longer gas tube interface (i.e., longer than the gas tube interface of the gas key 205) to accommodate the shorter barrel gas tube 224 of FIG. 31 (i.e., “shorter” referring to the barrel gas tube 224 of FIG. 31, which lacks the projecting gas tube segment 200A of the prior art FIG. 25). But preferably the gas key 210 comprises interfacing features that replicate features of the prior art gas key 205, thereby permitting the gas key 210 to properly interface with a stock bolt carrier (at the bolt carrier attachment interface 210A) and to properly interface with the barrel gas tube (at the gas tube attachment interface 210B).

FIG. 29 illustrates an upper receiver 214 that has been modified from a conventional prior art upper receiver by enlarging a diameter of an opening 216 to permit the gas key 210 (see FIG. 28) to pass therethrough. A user can easily enlarge the opening 203A in a prior art receiver 203 to accept the longer gas key 210 of FIG. 28.

FIG. 30 illustrates the upper receiver 214 with a portion of the gas key 210 protruding through the opening 216. This protruding segment is connected to the barrel gas tube, which has been shortened when compared to a prior art barrel gas tube. When the barrel coupler 113 (see FIGS. 10 and 18) is installed on the upper receiver 214 the protruding segment of the gas key 210 is received within the opening 29 (see FIGS. 10 and 18) in the barrel coupler.

FIG. 31 illustrates the gas tube 224 of the present invention, which is shorter than the prior art gas tube 220 of FIG. 25.

This invention (or a kit embodying the features of the invention) allows a user who has already purchased a removable barrel system to “upgrade” the rifle to one that is much less susceptible to damage while transporting or installing in the receiver.

The inventive components can also be sold by weapon manufacturers who currently sell prior art barrel systems with a gas tube that extends beyond the barrel's end. Such barrels absent the protruding end segment would undoubtedly be favorably considered by weapon owners.

Because the components of the present invention can be added to an existing rifle without modifying the existing rifle, these components can be easily removed and the rifle returned to its original configuration whenever desired. This is an advantage to the rifle owner who may wish to sell or trade-in a rifle that has been modified to implement the features of the present invention.

While the invention has been described with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalent elements and process steps may be substituted for elements and steps thereof without departing from the scope of the present invention. The scope of the present invention further includes any combination of the elements and process steps from the various embodiments set forth herein. In addition, modifications may be made to adapt a particular situation to the teachings of the present invention without departing from its essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

What is claimed is:
 1. A kit for use with a modular weapon having a barrel and an upper receiver, the upper receiver defining a gas port and a barrel opening, the kit comprising: an upper receiver coupler for attaching to the upper receiver; a barrel coupler; one or more first components for removably attaching the upper receiver coupler and the barrel coupler; the barrel for passing through a first opening of the barrel coupler, through a second opening of the upper receiver coupler, and into the barrel opening in the upper receiver; one or more second components for securing the barrel within the first opening of the barrel coupler; a gas key extending from the upper receiver and received within a third opening of the receiver coupler; and a gas tube connected to the barrel, extending rearwardly along the barrel, passing through a fourth opening in the barrel coupler and connected to the gas key.
 2. The kit of claim 1 wherein the modular weapon comprises a modular rifle.
 3. The kit of claim 1 wherein the one or more second components for securing the barrel within the first opening of the barrel coupler comprise threaded members threadably engaged in the barrel coupler and urged against the barrel.
 4. The kit of claim 1 the upper receiver comprising an upper receiver extension, the barrel opening defined therein, the upper receiver extension received within the second opening of the upper receiver coupler, the kit further comprising a nut for attaching the upper receiver coupler to the upper receiver extension with the nut having internal threads for threadably engaging external threads of the upper receiver extension.
 5. The kit of claim 1 wherein the one or more first components comprise one or more latches disposed on one of the upper receiver coupler and the barrel coupler for capturing one or more respective capture devices disposed on an other of the upper receiver coupler and the barrel coupler.
 6. The kit of claim 5 wherein the one or more latches comprise first and second hooks spaced apart at 180 degrees along a circumference of the barrel coupler, and wherein the one or more capture devices comprise a first pin and a second pin spaced apart at 180 degrees along a circumference of the upper receiver coupler, the first and second pins for capturing respective first and second hooks.
 7. The kit of claim 5 wherein the one or more latches each comprises a hook operated by a lever, and the one or more capture devices each comprise a pin, and wherein application of a force on the lever moves the hook to removably capture the pin.
 8. The kit of claim 1 wherein the one or more first components comprise: first and second pins attached to the barrel coupler; first and second shafts each having a first end attached to and rotatable about respective first and second pins; first and second heads attached to a second end of respective first and second shafts; and the first and second shafts captured within respective first and second recesses of the upper receiver coupler and held within the respective first and second recesses by the respective first and second heads exerting a force directed against a surface of the upper receiver coupler.
 9. The kit of claim 1 the barrel coupler further comprising a threaded member extending from a front surface of the barrel coupler for threadably engaging a hand guard such that the hand guard surrounds at least a segment of the barrel.
 10. The kit of claim 1 wherein one of the upper receiver coupler and the barrel coupler comprises an alignment pin for engaging an alignment opening in an other of the upper receiver coupler and the barrel coupler when the upper receiver coupler is removably attached to the barrel coupler.
 11. The kit of claim 1 further comprising a plurality of barrels of differing lengths, a forward end of the gas tube for attaching to one of the plurality of barrels with a gas block.
 12. The kit of claim 1 the gas key further comprising a bolt carrier attachment interface for attaching to the upper receiver and a gas tube attachment interface for attaching to the gas tube.
 13. The kit of claim 12 the gas tube attachment interface comprising a tubular segment protruding forwardly out from the upper receiver, the tubular segment received within the third opening of the receiver coupler and comprising the gas tube attachment interface for attaching to the gas tube.
 14. The kit of claim the gas tube shorter than the barrel.
 15. A system for connecting a barrel to an upper receiver of a modular rifle, the upper receiver comprising an upper receiver extension, the system comprising: an upper receiver coupler defining a first opening therethrough for receiving the upper receiver extension, the upper receiver extension removably secured within the first opening; a barrel coupler; a gas tube for attaching to a forward segment of the barrel, extending rearwardly along the barrel, passing through a second opening of the barrel coupler and for coupling to a gas port disposed in the upper receiver; the barrel for passing through and removably secured within a third opening of the barrel coupler, the barrel further passing through the first opening of the upper receiver coupler and for receiving within the upper receiver extension; and a component for removably connecting the upper receiver coupler and the barrel coupler.
 16. The system of claim 15 a length of the gas tube less than a length of the barrel.
 17. The system of claim 15 wherein the gas port comprises a gas key further comprising a bolt carrier attachment interface for attaching to a bolt carrier of the upper receiver and a gas tube attachment interface for coupling to the gas tube, the gas tube attachment interface further comprising a tubular segment protruding forwardly out from a fourth opening of the receiver coupler, the tubular segment comprising the gas tube attachment interface for attaching to the gas tube.
 18. The system of claim 15 wherein the barrel is removably secured within the third opening of the barrel coupler by a plurality of threaded members threadably engaged in the barrel coupler and urged against the barrel.
 19. The system of claim 15 wherein the component for removably attaching the upper receiver coupler and the barrel coupler comprises one or more latches disposed on one of the upper receiver coupler and the barrel coupler for capturing one or more respective pins disposed on an other of the upper receiver coupler and the barrel coupler.
 20. A weapon comprising: an upper receiver defining a gas port and a barrel opening, the barrel opening extending through a threaded upper receiver extension; a barrel; an upper receiver coupler, the threaded upper receiver extension extending through a first opening defined in the upper receiver coupler; a threaded component for threadably engaging and attaching the threaded upper receiver extension to the upper receiver coupler and thereby to the upper receiver; a barrel coupler defining a second opening for receiving the barrel, the barrel secured within the second opening and into the barrel opening in the upper receiver extension; a gas tube having a length less than a length of the barrel; a gas key having a first end attached to the upper receiver and a second end extending into a third opening defined in the receiver coupler; a forward end of the gas tube attached to a forward end of the barrel; a rearward end of the gas tube extending through a fourth opening in the barrel coupler and attached to the second end of the gas key for creating a continuous gas flow path from the forward end of the barrel to the upper receiver; and the upper receiver coupler attached to the barrel coupler. 